Optical Network Control: Architecture, Protocols, and Standards

3.3. Link Capacity Adjustment Scheme

Virtual concatenation allows the flexibility of creating SONET/SDH pipes of different sizes. The Link Capacity Adjustment Scheme or LCAS [ITU-T01a] is a relatively new addition to the SONET/SDH standard. It is designed to increase or decrease the capacity of a Virtually Concatenated Group (VCG) in a hitless fashion. This capability is particularly useful in environments where dynamic adjustment of capacity is important. The LCAS mechanism can also automatically decrease the capacity if a member in a VCG experiences a failure in the network, and increase the capacity when the fault is repaired. Although autonomous addition after a failure is repaired is hitless, removal of a member due to path layer failures ...